Los Angeles daily herald., 1887-05-18

less than one nunOreu shiious per uaS III
dowing through sewers provided for one
hundred and fifty gallons per day that no
deposits are 10 be feared with the smaller
amount.
1. therefore, iudorse tho recommendation
that provision be made for the large volume
III one hundred and fifty gallons per person,
II the supply is to remain abundant
f5.) The question OF the extent Of the fu-
iufe population of your city is one with
which am not qualified to deal. 1t seems
to me that all that 1t Is strictly necessary to
regard, aside from the question Of cost, Is
the regulation OF the size OF the sewers to
the ability OF the how to keep them clean.
Asa very large proportion OF your sewers
will be lsid with steep inclination ana
and as even the fiatter areas Of the
eli ~ have almost invariably good fall. !
feel confident that proper regulation or
sizes and flushing facilities will maintain a
perfectly good condition even though the
pf pulation may not exceed one hundred
thousand. 1t seems, therefore, perfectly
safe to leave tho discussion of the question
OF the extent of population to yourselves
Sewers constructed for two hundred thous-
and people would not be overcfowded, ex-
cept as to the main outlet. by population
Of three hundred thousand. so that deter.
minatiOn in favor of that amount would
seem to answer ali possible conditions.
With the imperfect data now in possession
OF your surveying department, it would be.
of course. impossible to determine the de.
tails OF the different parts of the system. l
would suggest, however. for your consider
alton, the following points:
a. The division Of the city according to
Typographical Indications into numerous
small ristricts; the combustion of these
districts into larger sub-main districts. and
the final concentration OF these sub-msin
districts at a general point OF out-fall a; the
southwestern corner of the city as suggested.
(2) Ample experience has shown that
properly laid aud properly regulated six.
inch pipes are ample for the discharge of
the sewage of very considerable district;
also, that such pipes, when properly laid
are not su ject to obstruction TO degree
thst need be considered for example, In
Keene. New Hampshire, where there are
more than ten miles OF six-inch pipes i'll
regular use, there has not been u single OBJ
struction due 10 the introduction of foreign
substances since the original construction
in 1852. With your more raIid INCLINATION.
liability to obstruction would be even less.
l would therefore suggest the use of these
pipes III all cases where their use BY
dense population in the districts that they
serve would not fill them at any hour of the
day more than half full, Below such points.
the sizs should be increased to eight
inches, ten inches, and larger, as the in
ereasing flow may require.
49, have strong opinion, based Oh
ample experience and observation, that II
is better not to use msn-holes on sewers
smaller than ten inches In diameter. be-
lieve that man holes are much more likely
10 be means of obstruction BY the intro
duction through them Of dirt, rubbish srti
cles that 1t NAV he desired TO get rid of.
tuan TO be useful in the removal OF such
obst uctions.
There is now available for the inspection,
the flushing and the cleansing of these
small sewers very simple devise by which
access is gained from the surface, through
inclined branch inspection pipes. looking
both up and down the line. II these are
placed at intervals of three hundred feet
Il will be easy to reach any roiut of the
sewer With heavy cleaning wires or flexi
BILE rods.
Man holes should be used on sewers ten
inches in diameter and larger: but even
these, up to a size Of at least fifteen inches.
should give access only to n covered open
ing in the pipe. so that matters falling or
thrown in from the surface caunot enter
the sewer, and so that the regularity of the
| flow may not be impedtd by the enlarge
mept at the n.hole as usually made.
think that changes of direction should
be made on curves of large radius, not AS
| has often been done by sharp curves within
the manhole Itself The facility for the in
| spection of the work by looking from one
manhole to another is of Ianciful rather
than real value. If the sewer can be seen
through in this manner, 1t needs no stten-
ton. II 1t needs attention because OF an
obstruction, II cannot be seen through. Its
condition can always be determined by the
use of cleaning rods or wires.
| 4. Throughout very large part of the
whole system of sewerage the natural flow
win be SUFFICIENT to remove deposits, but
such deposits are quite sue to be found
| near the upper ends of the lines, and here
the natural flow will not suffice TO sweep
these away before they shall have had time
10 putrefy and produce foul atmosphere
| IL has been ny custom, and has been found
most useful, to furnish the upper end of
every branch of the system with small
automatic flush tank. which may be fed
from the water supply or by the sewage
coming from few adjacent houses. This
suffices for maintaining cleanly condition
throughout the whole system.
(5.) The sewers should be ventilated
through house drains and soil pipes. The
drains should enter the sewer above the
flow line. There should be no traps in
their course nor in that of the soil pipes,
which should eud open-mouthed above the
roofs. Experience has shown that this sys-
tenn OF ventilation is unobiectionable and
entirely effective.
(6) There may he few instances in the
more level parts of the city where special
large flushing tanks fed by sewerage or
better. where convenient, from the irriea-
ton bitches. would de advantageous This
is detail which can be determined ly
in the perfecting OF the final plan.
The main outlet sewer will. at least for
some years, require heavy flushing Fortu-
nately this can easily be arranged by large
flush tank built ON the surface at or near
the beginning OF the out-fall drain, aud sup
piled from the irrigation ditch near by.
~ In my opinion IL would be better In
all cases to use circular sewers rather than
egg-shaped ones. The latter are use ful
chiefly where there is a great variation iu
the volume OF flow. due to the excess OF
rainwater. Where this is excluded, as II
would be in your case. the variation can
never be so great that ample additional
space will not be afforded by sewers of cir
cular section. Such sewers are cheaper ia
construction and are in all respects advisa-
Bile In your city.
(s) Much oil the difficulty Of this whole
case relates to the peculiar local conditions,
the outlying portions of the city bsing oil
such contorted grades that it will be impos
sible to lcca the sewers to the best ad van.
tage without much careful study In every
case in the completion OF the plan for for
sewerage This port of the work will re.
quire close consideration at the hands of
your City Surveyor. There Is no case where
it will not be easy to secure sufficient
grade ard a proper outfsll for every sec
| tion. but there are doubtless many cases
where an attentive study OF the relations OF
different parts of each district to each
other and to the whole scheme will not be
| necessary for the most satisfactory and
most economical disposition.
! (9) The whole plan being completed and
made In all respec's satisfactory, every
effort should be made to secure a close ad.
herence TO Il In the future. The whole sys
tenn cannot be completed for many years
but II would be a misfortune II future ad
ministrstions should change the plan, ever
in detail. unless after the fullest and mos
careful consideration, and with no other
motive than the public good In each In
| stance.
Perhaps II will be possible, in submitting
| the vote on the bonds for the work, TO limi
every expenditure 20 the exact carrying ou
| of the plan as submitted
Respectfully submitted,
GEO. +. WAEIHa. in.
San Francisco, Msy ID. 1887.